1. Field of the Invention
The present invention relates generally to a magnetic head assembly which is adapted to perfrom recording and reproduction on or from a flexible magnetic recording medium such as a magnetic tape. In particular, the invention concerns an improved active (or tape contacting) face configuration of the magnetic head assembly.
2. Description of the Prior Art
To have a better understanding of the invention, a hitherto known magnetic head assembly which the invention intends to improve will first be described in some detail. FIG. 1 of the accompanying drawings shows schematically in a perspective view a general structure of a magnetic head assembly destined to be used in conjunction with a flexible magnetic medium such as a magnetic tape, and FIG. 2 shows in a sectional view taken substantially along a single-dotted line II--II in FIG. 1 the structure of the magnetic head assembly in the vicinity of the tape-contact or active face portion thereof. It will be seen that the active head face which is positioned in opposition to the recording medium or tape is provided with a pair of supporting protrusions generally denoted by H which are juxtaposed with a space therebetween in the tape transporting direction and extend in the direction widthwise of the recording medium. The supporting protrusions H have surfaces brought into contact with the recording medium or tape and serve simultaneously to support the recording medium. Disposed within the magnetic head assembly internally of the supporting protrusions H are a number of magnetic cores exemplified by 7 and 8 which number corresponds to the number of the tracks to be formed on the recording medium, the magnetic cores 7 and 8 constituting parts of a recording head 1 and a reproducing head 2, respectively. A magnetic shield plate 6 is interposed between the recording heads 1 and the reproducing heads 2 for preventing magnetic leakage or cross-talk from occurring therebetween. The magnetic cores 7 and 8 are wound with coils 10 and 11, respectively, wherein the recording and the reproduction are effected through a recording gap 3 and a reproducing gap 4, respectively.
Lateral protrusions 16 play no part in the recording/reproducing operations and serve merely for facilitating the fabrication of the illustrated magnetic head assembly. These lateral protrusions 16 are of a substantially same configuration as that of the central supporting protrusions H.
It goes without saying that in order to obtain desirable recording/reproduction characteristics of the magnetic head assembly, the contacting state of the magnetic head with the recording medium as well as the floating state thereof has to be optimized and stabilized. In this connection, it is known that the contacting state of the magnetic head with the magnetic tape 9 and the floating state thereof can be optimized by selecting appropriate values for the factors R, L and .alpha. illustrated in FIG. 2, wherein the factor R represents a radius of curvature of the tape-contacting face of the magnetic head, L represents the width of the magnetic head in the transporting direction of the magnetic tape 9, and .alpha. represents an angle formed between the magnetic tape 9 and a tangent to the top of the active face of the magnetic head. By the way, the tape transporting direction is indicated by an arrow D in FIG. 2.
FIG. 3 shows, by way of example, an active face configuration of a hitherto known magnetic head (refer to Japanese Utility Model Application Laid-Open No. 174118/1981) in a sectional view taken along the recording gap 3 or the reproducing gap 4 in the direction widthwise of the magnetic tape. As will be seen in FIG. 3, grooves 5 are formed at such positions that the head width a (i.e. the width of the recording element or reproducing element array) is slightly narrower than that of the magnetic tape 9. The reason for providing these grooves 5 can be explained by the fact that unless the grooves 5 are provided, those portions of the recording and reproducing heads which are brought into contact with the edge portions of the magnetic tape 9 will be worn with a curvature due to abrasion, as is illustrated in FIG. 4, because the magnetic tape 9 is transported in contact with the magnetic head constantly over a predetermined region. As the consequence, the tape-contacting state of the magnetic head as well as the floating state of the tape will become unstable. With the provision of the grooves 5, it is intended to evade the shortcoming mentioned above.
In this conjunction, it should be mentioned that guide means (not shown) for guiding the magnetic tape 9 along both lateral edges thereof are usually provided in the vicinity of the magnetic head for positioning properly the magnetic tape 9 relative to the magnetic head in the direction widthwise of the tape 9. Accordingly, even when the grooves 5 are provided, lateral edge portions of the magnetic tape 9 undergo inevitably more or less deformation due to the guide means, as is illustrated in FIG. 3 by broken lines, resulting in that the contacting state of the tape with the magnetic head becomes unstable. This instability of the contacting state will become more significant as the flexural rigidity of the magnetic tape is increased, providing thus a cause for degrading the magnetic recording/reproduction characteristics of the magnetic head.
The undesirable phenomenon mentioned above can be mitigated to some extend by decreasing the values R and/or L or increasing the angle .alpha.. However, these measures are not effective to any satisfactory degree, when the flexural rigidity of the magnetic tape 9 is high. To the contrary, when the configuration of the magnetic head is modified in the manner mentioned above, the abrasion of the magnetic head becomes significant, shortening eventually the use life of the magnetic head assembly.
FIG. 5 shows another example of the active face configuration of a hitherto known magnetic head (see Japanese Patent Publication No. 32131/1974) in a sectional view taken along the recording gap 3 or the reproducing gap 4 in the direction widthwise of the magnetic tape. This configuration differs from the one shown in FIG. 3 in that a plurality of slits 12 are formed between the individual head elements which constitute the recording or reproducing head.
It has been described that the recording and reproduction are effected in the state in which the magnetic head is in physical contact with the magnetic tape 9. This holds true only when observed macroscopically. However, when observed microscopically, an air gap 13 is produced because of a fine roughness of the surface of the magnetic tape as well as an intervention of air flowing in through the angular space defined by the aforementioned angle .alpha.. The purpose of providing the slits 12 resides in improving the contacting state between the magnetic tape and the magnetic head by reducing the air pressure in the air gap 13 by means of the slits 12 when the air gap 13 can not be controlled even by selecting appropriately the factors R, L and .alpha..
Since the slits 12 have to be formed between the adjacent head elements, respectively, limitation is inevitably imposed on the size of the slits. Besides, the slits must be formed in a uniform size independent of the positions thereof, namely, whether they are located at the center or middle portion or lateral or end portions of the head, so that the air pressure produced within the gap 13 is the same throughout all the slits. Consequently, the instability can not be evaded in the contacting state between the magnetic head and the magnetic tape 9 at both lateral sides due to deformation thereof, as is in the case of the magnetic head configuration described above in conjunction with FIG. 3.